Specific absorption rate, SAR is a measure of the amount of radio frequency energy that is absorbed by tissues in the human body and expressed in watts per kg (W/kg). The SAR measurement is used to determine the capability of wireless devices, such as cell phones including smart phones, cordless phones, Laptop or Notebook or Netbook and Tablet Devices, including hand-held tablets and devices that are designed primarily for interactive hand-held use next to or nearby the human body, PTT two-way radios and universal serial bus dongles transceivers complies with the safety standards or guidelines. Currently, user's who are concerned with the adequacy of the SAR requirement or intends to reduce the exposure to radio frequency places the relevant wireless device away from the head or body by using a speakerphone or hands-free accessory.
Existing compliance approval regulations on controlled telecommunications requires radio frequency devices specifically radio frequency based wireless device manufacturers to comply with safety standards or guidelines. For example, the Federal Communications Commission, FCC in the United States of America adopted guidelines and requires compliance with the 1.6 W/kg safety standards whereby testing of the wireless devices are conducted under conditions of maximum power usage. The compliance requirements are stringent and difficult to be complied by the wireless device manufacturers especially when these devices are used in close proximity to the body or head as these wireless devices incorporates numerous combinations of signal modulations, channel bandwidths, radio frequency power, frequency bands, data rates and multiple antenna transmission schemes which pose a concern on potential safety hazards of human exposure to radio frequency energy.
United States Patent Application Publication No. US 2013/0099956 A1 (US 956 Publication) entitled “Apparatus to Reduce Specific Absorption Rate” having a filing date of 24 Oct. 2011 (Applicant: LSI Corporation) relates to protective devices for protection of radio frequency energy specifically protective materials configured to absorb radiated energy of wireless communication devices. In the US 956 Publication, it is provided that a user is protected from potential health risks from emitted radio frequency energy from a wireless handset or other device by reducing Specific Absorption Rate, SAR of the device while avoiding, or even improving, the radiation pattern of the antenna through protective materials. The examples of protective materials as disclosed in the US 956 Publication includes a hat, cap or other covering of a device user's upper body which includes a dual-layer structure comprising of carbon-loaded, open cell foam with a metalized layer. Further, it is stated in the US 956 Publication that the dual-layer structure is embedded in, for example, a hat with the carbon loaded foam facing away from the user's head. The covering as provided in the protective material of the US 956 Publication provides for RF protection of the user to reduce SAR while maintaining good return loss characteristics which avoids a negative impact on the antenna radiation pattern of the wireless device.
United States Patent Application Publication No. US 2014/0051480 A1 (US 480 Publication) entitled “Mobile Phone Microwave Radiation Protection” having a filing date of 16 Aug. 2013 (Applicant: John Fred Cruz) relates to protection of mobile phone from microwave radiation. The invention as disclosed in the US 480 Publication is used to reflect and block significant levels of microwave radio signals directed out of the front of the mobile phone as microwave radio signals are used to transmit data or voice between mobile phone and cellular towers. The invention as disclosed in the US 480 Publication further provides a protective shield when the front of the mobile phone is held next to the head or body when microwave radiation absorption takes place into the body as the shield is place on the front of the phone.
Another published patent application, United States Patent Application Publication No. US 2015/0333788 A1 (the US 788 Publication) entitled “Mobile Terminal and Specific Absorption Rate Reduction Method” having a filing date of 20 Aug. 2013 (Applicant: ZTE Corporation) describes a mobile terminal and a method for reducing a specific absorption rate, in a precondition of ensuring high-quality communication, a SAR value is reduced and decreasing the radiation hazard of the mobile terminal to the human body and human head. Further, in the US 788 Publication, the mobile terminal includes a control unit which is connected to an input unit, a memory and a switch, an antenna group containing multiple antennas, and the switch connected to each antenna and the radio-frequency circuit; wherein the input unit is configured to detect a location of the mobile terminal relative to a user, and notify the control unit of the location; the memory is configured to store location-specific absorption rate corresponding information of each antenna; and the control unit is configured to according to the location, search the location-specific absorption rate corresponding information for a specific absorption rate of each antenna at the location obtained, select an antenna according to the specific absorption rate of each antenna at the location and control the switch to connect the selected antenna with the radio-frequency circuit.
As there is a concern on potential safety hazards of human exposure to radio frequency energy from wireless devices, there is a need for a system and method to address and reduce the exposure of human to radio frequency radiation.